When should you change a Jaw Liner?

• Change or rotate a jaw liner when there is less than 20% life left anywhere along the working face of the jaw liner.
• Swing and Fixed jaw liners do not normally wear at the same rate. The wear rate differs from application to application. Typically the ratio is 2 Fixed Jaw liners for every 3 Swing Jaw liners.

Why should you change a Jaw Liner?

• Excessively worn jaw liners place additional stresses in the crusher frames and bearings.
• Jaw Liners that are worn too thin can crack and damage the crusher body resulting in expensive repairs and prolonged downtime.
• Worn Jaw liners affect production and draw more power.

Figure 1 above:  Shows the Liner profile, H is the tooth height of a new liner and 20% of H is an indication of when to rotate the Jaw liner.

How do you extending the life of jaw liners?

• Ensure that the jaw chamber is choke fed. The level of material in the jaw should just be below the jaw stock deflection plate.
• Reduce volume of fines and wet material entering the crusher.

Figure 2 above:  Taken from Sandvik Jaw training presentation.  Red square shows the ideal feel material height for choke feeding.

Figure 3 above: The result of over feeding the Jaw chamber as well as excessively worn Jaw liners

What to inspect on Jaw Crusher bearings?

• Regularly check temperature of inner and outer swing stock bearings. It should never exceed 60 degrees centigrade in normal applications.
• Inspect labyrinth seals, they should always be lubricated to keep a dust seal.
• Check all fittings and grease hoses for leaks and damage.
• It is best where possible to grease Jaw stock bearings after a day’s shift while the bearings are warm and with the jaw at running speed.

Elevated temperatures can be due to:

• Over greasing
• Insufficient grease
• Bearing failure
• Jaw overloading, too high a crushing ratio or to tight closed side setting
• Incorrect grease

Figure 4 above:  Shows the use of a laser temperature gun to check bearing temperatures

Figure 5 above:  Taken from Sandvik Jaw training presentation.  The blue line shows the temperature range of a new jaw crusher brearings.  The red line indicated a problem with the bearings either over greasing or a potential bearing failure.

Work hardening of Jaw liners

This term refers to strengthening if the liner as it is pounded by the rock forces inside the crusher chamber. The strengthening occurs due to a change within the microstructure of the material on the liner surface. As the rock pounds the liner the microstructure dislocates and the structure becomes denser.

The denser structure provides more resistance to forces. The work hardening face is usually about 2-3 mm deep on the liner tooth profile. Liners with higher manganese content work harden in shorter period of time.

Tips for work hardening Jaw Liners:

• Reduce the amount of fines fed into the crushing chamber
• Run the Jaw at a larger CSS for a day with new liners
• Jaw crusher speed must run slow enough for the Jaw liners to bite the material but not too fast that the material rubs the jaw liner teeth.
• Early rotation of the Jaw liners will assist in work hardening